The Polar Vortex may have been a week early. If you thought the recent Arctic blasts increased your chances for a white Christmas, you may be sorely disappointed.

After a frigid couple of weeks across the eastern half of the U.S., a warmer shift is anticipated this week and into the upcoming holiday weekend, said AccuWeather meteorologist Brett Rossio.

Still, it'll remain cold enough in much of the western mountains, northern Plains, Upper Midwest, Great Lakes and interior sections of the Northeast to retain snow cover through the weekend, thereby securing a white Christmas, the Weather Channel said.

More snow is also forecast to fall in some of those regions this week from a pair of winter storms forecast to track across portions of the northern tier of the country.

A quick-hitting system on Wednesday and Thursday will add a few more inches of snow from the northern Plains to northern New England, but milder air will be quick to return for the weekend, said AccuWeather meteorologist Max Vido.

However, warmer temperatures in the central and eastern U.S. will continue to erode the existing snow cover, Vido added.

On Christmas Eve and Christmas Day, temperatures should be above average for much of the eastern two-thirds of the nation, AccuWeather said. Places like New York City and Philadelphia will challenge 50 degrees. Across the South, temperatures will be mainly in the 60s and 70s.

Christmas Day travel troubles are possible in the central U.S. due to a storm that will mainly bring rain to cities such as Chicago, St. Louis and Dallas. There is even a risk for severe thunderstorms across the south-central U.S. on Christmas Day, the Storm Prediction Center said.

Only the northern Rockies and northern Plains will see additional snow Christmas Day. Blizzard conditions are possible in the Dakotas and northwest Minnesota, the Weather Channel said.

Dreaming of a White Christmas?

It need not snow Dec. 25 to fit the National Weather Service's definition of a white Christmas: There just needs to be at least 1 inch of snow on the ground.

As of Tuesday, about 49% of the 48 contiguous U.S. states were snow-covered, mainly across the nation's northern tier, the weather service said.

The USA's fascination with a white Christmas dates back to 1942, when Bing Crosby first crooned the wistful song in the film Holiday Inn. Written by Irving Berlin, the song's lyrics bring out a romanticized image of Christmases past, "just like the ones I used to know." A second movie — White Christmas, also with Crosby — came out in 1954.

Despite Crosby's wishes, only 25% to 30% of the 48 contiguous states are typically snow-covered by Christmas, according to AccuWeather.

Looking for a surefire way to get a white Christmas? Head to Fairbanks, Alaska, which has seen snow on the ground every Christmas since weather record keeping began, according to data from NOAA's National Centers for Environmental Information (NCEI).

In the lower 48, your best shot is in Minnesota; Maine; upstate New York; the Allegheny Mountains of Pennsylvania and West Virginia; practically anywhere in Idaho; and of course, the Rockies or the Sierra Nevada Mountains, NOAA said.

Historically, much of northern Minnesota and Wisconsin, most of Michigan's Upper Peninsula and a large portion of the Western mountain areas have a 90% or better chance of a white Christmas. Cities such as Marquette, Mich., or International Falls, Minn., have had snow on the ground almost every Christmas since weather record-keeping began, according to the NCEI.

Some of the biggest cities with the best probability for a white Christmas, based on historical averages, include Minneapolis, Green Bay, Buffalo, and Burlington, Vt., according to AccuWeather.

Historic probability of having at least one inch of snow on the ground on Christmas.(Photo: NOAA NCEI)